In one four-hour stretch, the nation’s political polarization was on stark display.

Just after 10 o’clock Tuesday morning, the Supreme Court struck down a key provision of the Voting Rights Act. To the ire of Democrats, Republicans in several Southern states moved to impose voter identification laws that had been delayed under the law.

Hours later, President Barack Obama announced a series of executive actions to combat climate change. Republicans cried foul.

Those moves on voting rights and climate change show how Republicans and Democrats tack toward their core constituencies. That generates a polarized dynamic that has largely deadlocked the government.

Analysts say the dysfunction can be blamed on the tendency of political parties that were once coalitions of different political types to sort themselves out by ideological lines.